Hypotonia in infancy (Floppy infant)
Hypotonia in infancy raises suspicion of an underlying neuromuscular disease, but acutely unwell children are also floppy and lethargic.
Causes of hypotonia are grouped as:
CENTRAL causes:
– Hypothyroid
– Down’s Syndrome
– Prader-Willi
– Inborn Errors of Metabolism
– Cerebral dysgenesis
Other:
– Prematurity, Sepsis
– Hypoxic Ischaemic Encephalopathy
– Maternal opiates
PERIPHERAL causes:
Anterior Horn cell disease
– SMA
– Pompe
Peripheral Nerve
– Inflammatory – GBS
– Demyelinating / Axonal
– Metabolic- Leigh
Neuromuscular Junction
– Myasthenias
– Infantile botulism
Muscle disorders
– Congenital Myopathy
– Muscular dystrophy
– Myotonic dystrophy
History key enquiries:
– Feeding issues?
– Breathing issues?
– Seizures? Dysmorphism?
– Developmental progress
Mother:
any illness, fever, substance abuse
Pregnancy
polyhydramnios,
reduced foetal movt, or malpresentation
Delivery
complicated/ prolonged, trauma, APGAR;
Family history
delayed milestones, weakness, myotonia
Examination GENERAL:
Is neonate preterm/ unwell / septic?
HIE features? Pale? Bruised?
Is term neonate requiring NG feeds?
Any obvious congenital anomaly-
external? Midline defects? hypogonadism or hypospadias?
RS: Resp- rate? Diaphragmatic movt? Good cry?
CVS: Cardiomegaly? Murmur? Femorals?
Abdo: Organomegaly? Underdeveloped scrotum?
Examination NEUROLOGY:
Alertness- encephalopathic?
Eye movements- able to fix & follow?
Facial muscle movements
Suck & swallow, tonge movements / fasciculations
Spontaneous fisting or an abnormal primitive reflex?
Posture, including tone
Spontaneous movt- more proximal / distal?
Any anti-gravity movements? Weakness?
Deep tendon reflexes
Plantar reflexes (esp if over 1y age)
Investigations:
Common early tests:
Bloods: Electrolytes, Mg, Ca, Glucose, CK
Metabolic: pH, Lactate, Pyruvate, NH3, S.AA, TFT’s;
Urine Organic acids & Amino acids
MRI Brain imaging
Karyotype (Microarray) & Gene testing- SMA, PWS
Further specialist tests:
CSF neurotransmitters,
VLCFA, other genetic tests,
auto-antibodies, etc
Electromyography /Nerve Conduction
Muscle biopsy
MR spectroscopy
Management principles:
– Reach definitive diagnosis to plan management & give prognosis
– Management of associated congenital anomaly/ cardiac dysfunction
Respiratory support – ? non-invasive ventilation and/or tracheostomy prevention (influenza and pneumococcal vaccination) and prompt treatment of respiratory infections
Orthopaedic intervention for joint contractures / postural deformities
Support Feeding – nasogastric feeding, caloric supplementation, gastrostomy?
Physiotherapy – aimed at prevention of contractures & deformities
Occupational therapy – improvement of function; consider appliances
Early intervention with developmental care and stimulation of learning